/*
 * Copyright 2015 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.handler.codec.http.cookie;

import static io.netty.handler.codec.http.cookie.CookieUtil.add;
import static io.netty.handler.codec.http.cookie.CookieUtil.addQuoted;
import static io.netty.handler.codec.http.cookie.CookieUtil.stringBuilder;
import static io.netty.handler.codec.http.cookie.CookieUtil.stripTrailingSeparator;
import static io.netty.util.internal.ObjectUtil.checkNotNull;

import io.netty.handler.codec.DateFormatter;
import io.netty.handler.codec.http.HttpConstants;
import io.netty.handler.codec.http.HttpRequest;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

/**
 * A <a href="http://tools.ietf.org/html/rfc6265">RFC6265</a> compliant cookie
 * encoder to be used server side, so some fields are sent (Version is typically
 * ignored).
 *
 * As Netty's Cookie merges Expires and MaxAge into one single field, only
 * Max-Age field is sent.
 *
 * Note that multiple cookies are supposed to be sent at once in a single
 * "Set-Cookie" header.
 *
 * <pre>
 * // Example
 * {@link HttpRequest} req = ...;
 * res.setHeader("Cookie", {@link ServerCookieEncoder}.encode("JSESSIONID", "1234"));
 * </pre>
 *
 * @see ServerCookieDecoder
 */
public final class ServerCookieEncoder extends CookieEncoder
{

    /**
     * Strict encoder that validates that name and value chars are in the valid
     * scope defined in RFC6265, and (for methods that accept multiple cookies)
     * that only one cookie is encoded with any given name. (If multiple cookies
     * have the same name, the last one is the one that is encoded.)
     */
    public static final ServerCookieEncoder STRICT = new ServerCookieEncoder(
            true);

    /**
     * Lax instance that doesn't validate name and value, and that allows
     * multiple cookies with the same name.
     */
    public static final ServerCookieEncoder LAX = new ServerCookieEncoder(
            false);

    private ServerCookieEncoder(boolean strict)
    {
        super(strict);
    }

    /**
     * Encodes the specified cookie name-value pair into a Set-Cookie header
     * value.
     *
     * @param name the cookie name
     * @param value the cookie value
     * @return a single Set-Cookie header value
     */
    public String encode(String name, String value)
    {
        return encode(new DefaultCookie(name, value));
    }

    /**
     * Encodes the specified cookie into a Set-Cookie header value.
     *
     * @param cookie the cookie
     * @return a single Set-Cookie header value
     */
    public String encode(Cookie cookie)
    {
        final String name = checkNotNull(cookie, "cookie").name();
        final String value = cookie.value() != null ? cookie.value() : "";

        validateCookie(name, value);

        StringBuilder buf = stringBuilder();

        if (cookie.wrap())
        {
            addQuoted(buf, name, value);
        }
        else
        {
            add(buf, name, value);
        }

        if (cookie.maxAge() != Long.MIN_VALUE)
        {
            add(buf, CookieHeaderNames.MAX_AGE, cookie.maxAge());
            Date expires = new Date(
                    cookie.maxAge() * 1000 + System.currentTimeMillis());
            buf.append(CookieHeaderNames.EXPIRES);
            buf.append((char) HttpConstants.EQUALS);
            DateFormatter.append(expires, buf);
            buf.append((char) HttpConstants.SEMICOLON);
            buf.append((char) HttpConstants.SP);
        }

        if (cookie.path() != null)
        {
            add(buf, CookieHeaderNames.PATH, cookie.path());
        }

        if (cookie.domain() != null)
        {
            add(buf, CookieHeaderNames.DOMAIN, cookie.domain());
        }
        if (cookie.isSecure())
        {
            add(buf, CookieHeaderNames.SECURE);
        }
        if (cookie.isHttpOnly())
        {
            add(buf, CookieHeaderNames.HTTPONLY);
        }

        return stripTrailingSeparator(buf);
    }

    /**
     * Deduplicate a list of encoded cookies by keeping only the last instance
     * with a given name.
     *
     * @param encoded The list of encoded cookies.
     * @param nameToLastIndex A map from cookie name to index of last cookie
     *        instance.
     * @return The encoded list with all but the last instance of a named
     *         cookie.
     */
    private static List<String> dedup(List<String> encoded,
            Map<String, Integer> nameToLastIndex)
    {
        boolean[] isLastInstance = new boolean[encoded.size()];
        for (int idx : nameToLastIndex.values())
        {
            isLastInstance[idx] = true;
        }
        List<String> dedupd = new ArrayList<String>(nameToLastIndex.size());
        for (int i = 0, n = encoded.size(); i < n; i++)
        {
            if (isLastInstance[i])
            {
                dedupd.add(encoded.get(i));
            }
        }
        return dedupd;
    }

    /**
     * Batch encodes cookies into Set-Cookie header values.
     *
     * @param cookies a bunch of cookies
     * @return the corresponding bunch of Set-Cookie headers
     */
    public List<String> encode(Cookie... cookies)
    {
        if (checkNotNull(cookies, "cookies").length == 0)
        {
            return Collections.emptyList();
        }

        List<String> encoded = new ArrayList<String>(cookies.length);
        Map<String, Integer> nameToIndex = strict && cookies.length > 1
                ? new HashMap<String, Integer>() : null;
        boolean hasDupdName = false;
        for (int i = 0; i < cookies.length; i++)
        {
            Cookie c = cookies[i];
            encoded.add(encode(c));
            if (nameToIndex != null)
            {
                hasDupdName |= nameToIndex.put(c.name(), i) != null;
            }
        }
        return hasDupdName ? dedup(encoded, nameToIndex) : encoded;
    }

    /**
     * Batch encodes cookies into Set-Cookie header values.
     *
     * @param cookies a bunch of cookies
     * @return the corresponding bunch of Set-Cookie headers
     */
    public List<String> encode(Collection<? extends Cookie> cookies)
    {
        if (checkNotNull(cookies, "cookies").isEmpty())
        {
            return Collections.emptyList();
        }

        List<String> encoded = new ArrayList<String>(cookies.size());
        Map<String, Integer> nameToIndex = strict && cookies.size() > 1
                ? new HashMap<String, Integer>() : null;
        int i = 0;
        boolean hasDupdName = false;
        for (Cookie c : cookies)
        {
            encoded.add(encode(c));
            if (nameToIndex != null)
            {
                hasDupdName |= nameToIndex.put(c.name(), i++) != null;
            }
        }
        return hasDupdName ? dedup(encoded, nameToIndex) : encoded;
    }

    /**
     * Batch encodes cookies into Set-Cookie header values.
     *
     * @param cookies a bunch of cookies
     * @return the corresponding bunch of Set-Cookie headers
     */
    public List<String> encode(Iterable<? extends Cookie> cookies)
    {
        Iterator<? extends Cookie> cookiesIt = checkNotNull(cookies, "cookies")
                .iterator();
        if (!cookiesIt.hasNext())
        {
            return Collections.emptyList();
        }

        List<String> encoded = new ArrayList<String>();
        Cookie firstCookie = cookiesIt.next();
        Map<String, Integer> nameToIndex = strict && cookiesIt.hasNext()
                ? new HashMap<String, Integer>() : null;
        int i = 0;
        encoded.add(encode(firstCookie));
        boolean hasDupdName = nameToIndex != null
                && nameToIndex.put(firstCookie.name(), i++) != null;
        while (cookiesIt.hasNext())
        {
            Cookie c = cookiesIt.next();
            encoded.add(encode(c));
            if (nameToIndex != null)
            {
                hasDupdName |= nameToIndex.put(c.name(), i++) != null;
            }
        }
        return hasDupdName ? dedup(encoded, nameToIndex) : encoded;
    }
}
